'Redirect to SMB': an old Windows bug that back in the spotlight

Cylance has discovered a ‘new’ vulnerability in Windows, a weakness that was never patched by Microsoft.


The bug, called “Redirect to SMB,” is a variant of a vulnerability found in Windows by Aaron Spangler 18 years ago: this cause the exposition of a user’s Windows username and password.

From Cylance website:

Redirect to SMB is a way for attackers to steal valuable user credentials by hijacking communications with legitimate web servers via man-in-the-middle attacks, then sending them to malicious SMB (server message block) servers that force them to spit out the victim’s username, domain and hashed password.

and about the original vulnerability:

The Redirect to SMB attack builds on a vulnerability discovered in 1997 by Aaron Spangler, who found that supplying URLs beginning with the word “file” (such as file:// to Internet Explorer would cause the operating system to attempt to authenticate with a SMB server at the IP address

Affected applications?

In his white paper, Cylance says that are 31 applications vulnerable to this flaw:

Widely Used Applications:

  • Adobe Reader
  • Apple QuickTime
  • Apple Software Update (which handles the updating for iTunes)

Microsoft Applications:

  • Internet Explorer
  • Windows Media Player
  • Excel 2010, and even in Microsoft Baseline Security Analyzer


  • Symantec’s Norton Security Scan
  • VG Free
  • BitDefender Free
  • Comodo Antivirus

Security Tools:

  • .NET Reflector
  • Maltego CE

Team Tools:

  • Box Sync
  • TeamViewer

Developer Tools:

  • Github for Windows
  • PyCharm
  • IntelliJ IDEA
  • PHP Storm
  • JDK 8u31’s installer

How do you protect yourself?

  • Block outbound traffic from TCP 139 and TCP 445.
  • Apply applicable and up-to-date software patches from vendors.
  • Use strong passwords so that it requires a larger time for brute forcing of any hashing algorithms.

Published: April 15 2015